Ultra high frequency electronic device



Nov. 21, 1950 A. E. BOWEN ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed may 4, 1943 ll Sheets-Sheet 1 FIG 2 FIG. 4

and,

INVENTOR ,4. E BOWEN B) y WW ATTORNEY Nov- 1, 1950 -A. E. BOWEN 2,530,373

ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed May 4, 1945 l1 Sheets-Sheet 2 FIG. 5

lNl/EN ran A. E BOWEN aWM A TTORNE Y Nov. 21, 1950 v Filed May 4, 1943 A. E. BOWEN 2,530,373

ULTRA HIGH FREQUENCY ELECTRONIC DEVICE 11 Sheets-Sheet 4 FIG. 8

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{I ll 1: l

INVENTOR ,4. E BOWEN QWW A T TORNEV Nov. 21, 1950 r BOWEN 2,530,373

ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed May 4. 1943 ll Sheets-Sheet 5 FIG. 6/ m 9 I r I I m/ve/vron A. E. BOWEN A TTORNEY Nov. 21,. 1950 A. E. BOWEN 2,530,373

ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed May 4, 194a 11 Sheets-sheaf e v INVENTOR A. 5 BOWf/V VWM A TTORNEV Nov. 21, 1950 A. E. BOWEN 2,530,373

ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed May 4, 1943 ll Sheets-Sheet 7v INVENTOR A E BOWEN ATTORNEY Nov. 21, 1950- A. BOWEN 2,530,373

' ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed May 4, 1943 11 Sheets-Sheet a FIG/.9 was, 971

MAG/V5776 F/ELD amrcrzo PAP/1L L a IN l E N TOR A. 'E BOWEN I av OWM A T TORNE V Nov. 21, 1950 A. E. BOWEN 2,530,373

ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed May 4, 1943 ll Sheets-Sheet 9 FIG. 20

lNl EN TOR A. E BOWEN GWM A TTORNEY Nov. 21, 1950 A. E. BOWEN- 3 4 ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Filed May 4, 1943 11 Sheets-Sheet 1o FIG. 22

[ll Wik T0 VA GUUM PUMPING 5 Y5 TE M INVENTOR A. E. BOWEN VWW ATTORNEY Nov. 21, 1950 A. E. BOWEN ULTRA HIGH FREQUENCY ELECTRONIC DEVICE ll Sheets-Sheet 11 Filed May 4, 1943 Q to lNl/ENIOR ,4. E BOWEN A 7' TORNE Y Patented Nov. 21, 1950 ULTRA HIGH FREQUENCY ELECIRGNIC DEVICE ArnoldEaBowemRed Bank, N. .J .,-assignor..to-Bell Telephone Laboratories, Incorporated, ."New York, N. X, acorporation of New York Applicationlvlay l, 1943, Serial No. 485,579

9 Claims.

This invention relates toarrangeinents for effecting energy interchanges in high frequency electromagnetic systems particularly between a stream of moving charged particles such as electrons, and electromagnetic waves guidedor enclosed by electrical conductors.

"In devices of this typepit is common practice to determine the trajectories of the charged particles either by means of an electric field alone or by a combination of electric and magnetic field components. Devices in which the combined type of trajectory control is employed are commonly called magnetrons. In one known class of magnetrons an electric field is maintained by impressing a potential between parallel plane plates, while at'the same time a magnetic field is maintained parallel to the plates and hence perpendicular to the electric field. It is known that electrically charged particles upon being exposed to the action of mutually perpendicular electric and magnetic fields and having initial velocities confined to the direction perpendicular to both the electric and magnetic field intensity-vectors, move in cycloidal and trochoidal paths. In magnetrons with cycloidal or trochoidal electron trajectories, use has been made, as far as I am aware, only of that part of the energy residing in the transverse component of the electron velocity. In other words, the energy .utilizedhas been taken from the electron during the part of its motion perpendicular to the planes between which it moves.

It is a feature of the present invention that energy is abstracted from the electron when it is traveling parallel to the planes between which it moves. The invention may be embodied in oscillators, amplifiers, repeaters, and the like, particularly for high frequency and microwave applications, wherever generation, repetition, control or amplification of electromagnetic waves is an object.

In accordance with the invention, a stream of charged particles is constrained to move in a trajectory comprising a series of cycloidal or trochoiclal hops, progressing along a predetermined axis. The motion is characterized by the alternate intervals of relatively high forward axial speed and relatively low or reversed axial speed peculiar to cycloidal or trochoidal motion under substantially constant forces. The regions of relatively high axial speed may conveniently be designated as loops and *the intervals of relatively low or reversed axial speed as nodes, in partial analogy to the alternate loops and nodes of a vibrating air column. The stream of charged particles issubjected .to -a cyclical velocity variation followed byiaeseparation of accelerated and decelerated electrons to form a density varied stream which-may beused to excite oscillations in a resonator of suitable form. In accordance with the invention, the velocity variation and oscillation excitation operations are carried out atloops-inthe cycloidal path .while the stream is density varied by withdrawing some of the elec trons from the stream ina region near a nodal point-of the .path.

vI-t-has'already.been proposed toperform upon a stream cfcharged particles the operations of velocity variation, velocity sorting and energy abstraction in that order and at successivepoints along the path of the stream. It is also known that velocity sorting maybe eifected by variably curving or deflecting the stream. The arrangementsof the present invention, however, have-an advantage .not found in prior devices, namely that the path of the stream ,iskept. away from the vicinity of thedefiecting orcontrolling electrodes except at those points where the operations of velocity variation, remoyaliof unwantedparticles, and abstraction of energy are to be eifected. As a result, energy losses and noise currents caused by charged particles striking the deflecting or controlling electrodes are 'iargely avoided. Other features and advantages of the invention will be evident from the following description.

Several illustrative embodiments of the'invention aredescribefd in detail hereinafter with reference to the accompanying drawings, in which:

Fig. 1 is a somewhat diagrammatical crosssectional view vofa typical mechanism for corn trolling the trajectories of. a successionof charged particles in accordance with the invention;

Fig. 10 is a schematic diagram corresponding to Fig. 9;

Fig. 11 is a schematic diagram of an electron coupled oscillator-amplifier arrangement;

Figs. 12 to 17, inclusive, are perspective views of tuned circuit structures adapted for use in various embodiments of the invention;

Fig. 18 is a schematic diagram of another form of electron coupled oscillator-amplifier;

Fig. 19 is a perspective view in longitudinal section, showing a repeater in a wave guide transmission line;

Figs. 20 and 21 are perspective views, partly diagrammatic, showing other structures embodying the invention in an oscillator;

Fig. 22 is a perspective View, partially broken away, showing another embodiment of the invention in an oscillator;

Fig. 23 is a perspective view, in longitudinal section, showing another embodiment in an oscillator coupled to a wave guide;

Fig. 24 is a perspective view, partially broken away, showing an adaptation of the invention to utilize concentric cylindrical plates in place of plane parallel plates; and

Fig. 25 is a sectional view of the structure of Fig. 24.

The principles underlying the invention are conveniently explained with reference to Fig. 1 wherein are represented diagrammatically two parallel plane plates i and 2 separated a distance and maintained at a substantially constant potential difference V0, plate I being positive with respect to plate 2. The resultant electric field intensity acts downward in the plane of the drawing as indicated by arrows in the figure. A cathode 3 is located in the plane of plate 21 and may be insulated from the plate so that the cathode may be 3. directly heated filament if desired. Slots or gaps 4 and 5 are made in plate I on centers spaced apart a distance m, the slot 4 being located a horizontal distance from the cathode 3. A collector plate 6 is located in the plane of plate 2, insulated therefrom, and preferably maintained at a potential somewhat positive with respect to plate 2. A substantially uniform magnetic field of intensity H is maintained with its lines of force directed perpendicular to the plane of the drawing in the sense away from the reader. It is assumed for the purpose of the explanation that the uniformity of the fields E and H is not materially disturbed by any edge effects or by the presence of the cathode 3, the collector 6 or the slots 4 and 5. Assuming further that electrons are released with zero velocity at the cathode 3, then, according to known principles the electrons will travel in trajectories such as that shown in the curve 7, which is a common cycloid. The assumed conditions may readily be approximated in practice.

The equations of motion of an electron in the system of Fig. 1 are readily set up and the equations of the electron paths under given boundary conditions derived therefrom by conventional analytical methods. It is therefore deemed unnecessary to present a detailed solution and only the basic equations and final results are set down here.

4 Assuming a set of mutually perpendicular rectangular coordinate axes X, Y, Z, directed as indicated in Fig. 1, the equations of motion for an electron of charge e and of mass m are 61 x eH dz Zia-tea (P2 eE eHdx av amt a (3) where c is the velocity of light, and e, E, and H are tobe taken as positive numbers. The equations are adjusted for the Gaussian system of units, 6 and E being in electrostatic units, H in electromagnetic units, m in grams, distances in centimeters, time in seconds, and c in centimeters per second. As the problem is fundamentally one of two dimensions only, it will not be necessary to consider further the y-coordinate nor equation Additional simplification of the analysis may be had by introducing the following abbreviations:

eH P

the use of which makes eE E-"P 0 The equations to be solved then reduce to d x dz P d z da: E P( O The complete solution of the simultaneous equations (7) and (8) is a:=C sin ptC' cos pt+s t+C (9) z=C sin pt-l-C cos phi- 2 0) from which the following may be derived by differentiation:

In (9) to (14) inclusive, C1, C2, C3 and C4 stand for the constants of integration.

From the general solutions (9) and (10) a particular solution may be had for the case of particles starting from rest at the origin at the time when t is zero by using the initial conditions represented by to determine the constants of integration. The result is readily found to be (p -sin p 2:? (l--'cos pr 17,

the'standard equations of a common cycloid.

Referring to the curve Tin Fig. 1 the left-hand portion of the curve represents the common cycloid'of equations (16) and (17). The curve will have a maximum value of z for the condition pt=1r (18) and at this point it will be found that Assuming that the spacing a has been so chosen that the cycloidal trajectory i will just graze the plate I, it will be evident that the maximum z-coordinate of the trajectory will be equal to a and it will be found that at pt=1r,

In accordance with the invention, a velocity variation is impressed upon the particles as they pass the first point of maximum z-coordinate, by means of a variable potential diiference across the slot 4 which Will be suitably superposed upon theinitial potential V0 of the plate I as a whole. Then the potential which acts upon a given electron causing it to approach and pass the gap 4 may be expressed as where 6 is a small factor which in ordinary practice will usually lie within limits between 1 and +1. It will be evident from Fig. 1, that the initial potential V0 acts continually to accelerate the electrons towards the plate I while the magnetic field deflects the electron until upon reaching the gap l the electron is travelling substantially parallel to the plate I. The increment of potential represented by We is effective mainly in the immediate vicinity of the gap 4 and exerts a force upon the electrons in a direction substantially parallel to the plane of the plate I and hence in the direction of the motion of the electrons to accelerate or decelerate the electron brieflly while the electron is passing the gap 4. Thus the potentials V0 and V0 may properly be added algebraically to express the total effective potential V. If we assume that a given electron leaves the gap 4 with a speed 5 determined by the potential V as given in (26) then the equation Ve=%ms (27) represents therelationship between V ands based upon the conversion :of potential energy into kinetic energy. :So'lvi'n'g x27.) :for and using 26) gives Using Vo=aE (29) together "with (25) and (4), we have anvil? The trajectory o'f an electron after it'leaves'th'e gap 4 must be such as to satisfy the equationsof motion (1), (2) and '(3) as well as the new initial conditions produced by the velocity variation. The latter conditions are such that when Under these conditions it is readily found that Equations '(36) and (37) will berecognized as the equations of a family of trochoids generated by a movable point, distant from the center of a circle of diameter a which is rolling upon and above the line The trochoids corresponding respectively to the values -6=0.5, 5:0, and 6=+0.5 are plotted in Fig. las curves 8, 9 and I0. Curve 9 is-a commoncycloid, which is a special case of a trochoid.

Two important characteristics of the trajectories-are tobe deduced from the above analysis. The first is that all the trajectories regardless of the t-value pass througha common point near the gap 5. The second important deduction is that the average value of the x-velocity of each particle is equal to 80, independently of the t-value. In particular the result is found that the transit time between'the gaps '4 and 5 is the same for "all the particles regardless of the length and shape of trajectory. Boththese characteristics may .be verified by substituting pt=31r in (36) and (37) which gives which expressions are independent of 6 and determine the above-mentioned common point at the gap 5. The average speed of any particle while traversing the distance between the gaps 4 and is the intergap distance n-a divided by the transit time from pt=1r to pit-=3, which speed amounts to In accordance with the invention, the passage of charged particles across the gap 5 in a density varied stream causes an alternating current to be induced in the plate l. The stream is given a density variation by the action of the plate 2 which is so placed as to intercept particles in a group of trajectories represented. by curve H! while particles in a group of trajectories represented by curve 8 pass on unintercepted. The velocity variation impressed upon the stream at the gap l produces a cyclical variation in the trajectories of successive particles ranging in turn through trajectories of the type of curve 8, the cycloidal type 9, the type of curve Hi, the cycloidal type again and back to the type of curve 8, etc. Only the particles following trajectories of the type 8 reach the gap 5 and these form a density varied or intermittent stream at the gap 5. Plate 6 serves to collect the spent particles after they leave the gap 5. The parts of the curves 9 and H] which are unoccupied by particles because of interception by plate 2 are shown dotted in Fig. 1.

It will be noted that the mechanism described is one for transforming a steady stream of charged particles into an intermittent or density varied stream. It will be noted further that the grouping of, the, particles is not dependent upon the principle of fast moving particles overtaking slower moving particles. The principle employed is one of segregating those particles which exceed a certain critical velocity.

It will be noted further that the charged particles approaching the gap 4 are moving with substantially a uniform velocity and in a direction parallel to the plate i. This condition might be brought about in various ways other than by locating the cathode 3 in the plane of the plate 2 and using the mechanism described for producing the cycloidal trajectory I. For example, the stream of charged particles might be made to approach the gap t along a straight path parallel to the plate I under the influence of an electric field in the absence of the magnetic field H. The

mechanism shown and the use of the cycloidal trajectory I will ordinarily be simplest and most expedient, but it will be understood that it is within the scope of the invention to employ any suitable means to provide a stream of charged particles which approaches the gap 6 with substantially uniform velocity and charge density.

In any case, after leaving the gap c the motion of the particles is characterized by a periodic component of motion in the direction of the electric field superposed upon a general progression or drift in the direction perpendicular to the plane common to the electric and magnetic vectors. In the neighborhoods of gap 4 and gap 5 the periodic component of motion in the direction of the electric force has resulted in a maximum displacement in compliance with the electric field. In the region where certain of the trajectories meet the ground plate 2, the particles are moving in opposition to the electric field. In the case of trajectories of the type of curve IQ there is superosed upon the drift motion an incidental periodic component which could be utilized if circumstances warranted. a

The velocity variation at the gap 4 efi'ects a 8. control over the periodic motion in the direction of the electric force, namely a control of the amplitude of such periodic motion. Under the variable amplitude conditions, however, all the variation is confined to the region in which the particles move against the force of the electric field, as described, the excursion of the particles in compliance with the electric force being limited to the uniform maximum value a by the combined effect of the electric and magnetic fields.

In the operation of the device as an amplifier, the potential of the gap 4 is varied by means of the wave to be amplified and the output resonator is connected across the gap 5. The spacing 1rd between the gaps 4 and 5, as seen from (25), is a function of both E and H, varying directly as E and inversely as the square of H. The transit time between the gaps is and varies inversely with H, independently of E. There is, moreover, no critical transit time required in the amplifier case.

In the operation of the device as an oscillator, the available values of H are limited once the frequency of the desired oscillation is determined. It has been shown above that the particles which pass the gap 5 when the plate 2 is in place are those which are decelerated at the gap 4. In order for these particles to contribute energy to the field at the gap 5 the particles must pass gap 5 while the field is opposing their motion. 'In a case where the gaps 5 and 5 are excited in such manner that the fields at the two gaps are poled in the same direction, an integral number of periods of the oscillation should elapse between the passage of a particle across the gap 4 and its subsequent passage across the gap 5.

In the case of an amplifier, the gap 4 serves as an input gap to which an input resonator and a source of waves to be amplified may be coupled, while the gap 5 serves as an output gap to which an output resonator and a load may be coupled. In the case of an oscillator, which as is well known, generally comprises an amplifier with the input and output circuits thereof coupled together in regenerative relationship, the first gap 4 may still be regarded as an input gap inasmuch as the potential difference existing across this gap during oscillation acts upon the electron beam to impress thereon a velocity variation. The second gap 5 may also still be regarded as an output gap in an oscillator inasmuch as the electron beam passing this gap is primarily active to induce and maintain an alternating potential difference across the gap.

In terms of the frequency, f, the relation f p 8H must hold, where n is any integer, or, in terms of the free space wave-length, A,

2 21rmc in which formula x is to be expressed in centimeters, H in electromagnetic units and e in electm'static. units; The same thingwithelectromagnetic units. throughout is 21rmc 1L6 which, when the charged particles are electrons becomes approximately which formula is applicable either to an amplifier or an oscillator. Since in the case of the electron oscillator Al-I is. given by (45), the spacing are in electromagnetic units. is in centimeters,

and the velocity of light, c=3' 10 centimeter/seconds, or

centimeters where A is in centimeters and V in volts.

Anumber of examples comingout of formula (50) have been computed and are shown diagrammatically in Figs. 2, 3'and 4. It will be noted that for given values of.) andVO, the spacing ais proportional to n. Thus. if, as inFig. 2, a has the value or, correspondingto n=l then for the same wavelength and same voltage, the spacing is 2600 for 12:2, which case is shown in Fig. 3; and 3:10 for n=3, as shown in Fig. l. The spacing of the gaps is equal to 1rd in everycase. For a wavelength of lO'centimeters anda voltage V0 of 1,000 volts, the value of comes out approximately 1 millimeter.

Various changes in the values of V0 and H may be made, at the same time changing 12, so that the required spacing remains the same. For example,,in Fig. 2 if n is made 2 and the wavelength and spacing remainunehanged,the voltage must be reduced to one-fourth its former value. The change in n also requires that H be reduced to one-half its former value, in order that (4'7) may be satisfied;

Several possible combinationsv of values. for a 10 centimeter wavelength in the diagram of Fig. 2 are tabulated in Table I.

Several possible combinations for a 10 centimeter wave length in the diagram of Fig. 3' are given in Table II. I

it be decelerated at the gap 4, is indicated at 8' Table II a, cm. n Va, volts H, oersteds A, cm.

Combinations for the diagram of Fig. 4 are given in Table III.

Table III a, cm. n V0, volts H, oersteds A, cm

Conductors l4, l5 and IB' of a resonant circuit are shown schematically, connecting the plate segments I in Fig. 2. To indicate resonance at the same wavelength in Figs. 3 and 4 as in Fig. 2, the areas enclosed by the conductors are shown approximately equal in all three figures.

Fig. 5 represents an embodiment of the invention in an oscillator complete with a resonating circuit, an output coupling. device and means for supplying the requisite electric and magnetic field intensities. The equivalent of the plate I of Fig. 1 is represented in Fig. 5 by a three-segment anode having segments H, l2 and I3 connected together by conductors l4, l5 and It, the latter, together with the anode segments, comprising a resonant circuit. The inductance of the resonant circuit resides mainly in the conductors l4, l5 and i6 while the capacitance is mainly between segments Ii and I2 at the input gap 4 and between segments I2 and [3 at the output gap 5. The negative or ground plate 2" has a depression in which the cathode 3 is insulatingly mounted. These parts, together with the collector plate 6, are supported by rods held in a press ll of conventional type formed in the wall of a vacuum-tight container [8, which wall may, for example, be of glass. The supporting rods may serve also as electrical connections from the plates to the sources of electromotive force. The latter sources may constitute batteries or other suitable devices, of which 19 serves to heat the cathode, 28 to polarize the anode segments H, I2, l3 positively with respect to the ground plate 2, and 2i serves to maintain the collector 6 preferably at a somewhat positive potential with respect to the plate 2. Coupled to the conductors l4 and I6 is a coupling loop 22 the ends of which may project through the envelope ['8 and be connected to any suitable load device for transmitting utilizing the generated oscillations, the load circuit here being represented by a resistor 23. An electromagnet comprising pole-pieces 24, winding 25, a yoke 26- and energized by suitable means such as a battery 21, is provided preferably external to the envelope I 8 and is set up in such a position (Fig. 5A). as to provide a magnetic field having lines of force substantially parallel to the oath-- ode 3and the several plates.

The cycloidal path of a typical electron leaving the cathode 3 and approaching the gap 4 isshown at I. The path of this electron, should showing that its trajectory continues past the gap and preferably ends upon the collector plate 6. Should the same electron instead be accelerated at the gap 4 its path is indicated at In, ending upon the ground plate 2 and not reaching the gap 5.

The spacing between the ground plate and the anode is determined as described hereinbefore in connection with Fig. 1, for a desired operating wave-length at a given voltage and for a chosen value of n, according to (55). nator is proportioned to be resonant to the operating wave-length. Further details of the operation of the system of Fig. 5 will be evident from the explanation given hereinabove in connection with Fig. 1.

Figs. 6 and 7 show how the device of Fig. 5 may be modified to employ a cavity resonator. The anode segments H, i2 and I3 of Fig. 5 are replaced in Fig. 6 by the slotted end wall or plate 32 of a cavity resonator 34 which may be a section of a conductive-walled or hollow pipe wave guide. The slots in the plate 32 comprise an input gap 4 and an output gap 5. The resonant chamber may be bounded at the end oppoguide 31. The envelope 18 may be suitably sealed to the walls of the resonator 34 and the aperture 36 may be made vacuum-tight by a plug 38 of dielectric material. The length of the resonator 34 will ordinarily be approximately one-half wave-length of the desired oscillation frequency, the wave-length being that peculiar to the electromagnetic wave as propagated inside the wave guide rather than the free space wave-length. The resonator 34 will, of course, need to be of sufficiently large diameter to freely transmit a wave of the desired wave-length.

The modification shown in Fig. 7 employs a folded resonating chamber and may be preferred where it is desired to decrease the over-all length of the apparatus. The resonator 39 shown in Fig. 7 may have an over-all length Of approximately a quarter wave-length. A conductive partition 40 conductively connected to the plate 32 extends from side wall to side wall between the slots and nearly the full length of the resonator 39. A coupling loop 4i may be provided to deliver oscillations to an outgoing coaxial line.

Fig. 8 illustrates an embodiment of the invention in an amplifier. In the arrangement of Fig. 8 the conductor 15 used in Fig. 5 is replaced by a conductive plate 42. The conductors l4 and I6 are replaced respectively by conductors 43 and 44 connected to opposite sides of the plate 42. An input coupling loop 45 is arranged adjacent the conductor 43. The collector plate 6 may be insulatingly mounted upon a shoulder cut in the ground plate 2, as shown. Waves to be amplified may be supplied by a source 46 connected to the loop 45. The impressed oscillations serve to set up alternating potentials across the input gap 4. The amplified oscillations are set up in the resonant circuit including the conductor 44. A coupling loop 4? is mounted adjacent the conductor 44 and is connected to a load device 48. The detailed operation of the system of Fig. 8 as an amplifier will be readily understood from the description hereinabove given in connection with Fig. 1.

In an alternative mode of operation of devices in accordance with the invention, the faster The reso-.

group of electrons may be utilized in the excitation of the output circuit in place of the slower group. This mode of operation may be used with a small accompanying reorganization of the apparatus. Fig. 9 shows an amplifier arranged to eifect excitation of the output circuit by means of the faster group of electrons. The chief modification comprises the placing of the input and output circuits on opposite sides of the ground plate, in the form of separate anodes. Each anode may comprise two segments defining a single gap. It may be necessary in some cases to provide increased separation between the ground plate and the collector in order to accommodate the passage of accelerated electrons therebetween in a variety of trajectories.

In the arrangement of Fig. 9, a vacuum container is represented by the envelope 58. The leads by which the energizing and biasing potentials are applied to the various electrodes within the vacuum compartment are shown for simplicity by solid lines crossing the envelope 58. For simplicity, also, the energizing sources of electromotive force have been omitted since they maybe readily supplied as shown in Figs. 5 and 3. A cathode 5| is represented as supplied by heating leads 52 and 53. A ground plate 54 is provided with a groove for accommodating the cathode 5|. External connection to the ground plate is provided by means of a lead 55. A source of big) frequenc waves to be amplified is represented by a generator 56, coupled by means of a loop 5" to an input tuned circuit comprising two anodc segments 58, 59 joined by a conductor 6!! and defining an input gap between the segments 58 and 59. A suitable positive potential may be impressed upon the system 58, 59, 60 by means of a lead El preferably symmetrically disposed, as shown. A collector 62 is provided in the same plane as the ground plate 54 and is connected to a lead 63. On the opposite side of the ground plate from the system 58-450 is provided an out put tuned circuit comprising two anode segments 54, 65 joined by a conductor 66 and defining an output gap between the segments Stand 65. An output loop 6? is provided in inductive relation to the conductor 66 and has its ends led out to a load circuit which is represented by a resistor 68. A suitable positive potential may be impressed upon the anode system 64-66 through a lead 69. In the operation of the system of Fig. 9, the typical electron leaving the cathode 5! travels in a cycloidal trajectory l and in passing the vicinity ofthe input gap 58, 59 the electron receives a velocity variation due to the impressed waves from the generator 55 acting through the coupling system '5'! to 68, inclusive. The accelerated electrons pass through the gap between plates 54 and 62 and as they emerge they come into the field between the ground plate and the output anode system 54, 65, 65. An accelerated electron thus emerging follows a generally cycloidal trajectory 1'0 which carries it to the vicinity of the output gap between the anodesegments 64, '65 and finally causes the electron to strike the lower side of the plate 54 as shown. The decelerated electrons are carried past the gap between electrodes 54 and 62, to the collector 62. The accelerated electrons, thus separated from the decelerated electrons, form an intermittent or density varied stream which serves to excite the output tuned circuit as the stream passes the vicinity of the gap between electrodes 64 and 65.

r Fig. 10 is a simplified schematic representation 13. ofthezarrangement of Fig. 9', the elements. being correspondingl numbered in the. two figures.

Other modifications of the structures hereinabove. described enable the system to be adapted for use as amaster oscillator-amplifie combination in which the coupling between the oscillator and the amplifier is. effected by means of the electron stream. There is thus'provided' what is commonly termed an electron-coupled oscillator: Examples of this are shown in Figs. 11 and 18 by'means of simplified schematic representations.

In Fig. 11 there is shown, within a vacuum container H, a ground plate 12: having on one side thereof a cathode l3 and a tuned circuit 14 of the. three-segment anode type disclosed in Fig. 51 Coplanar' with the ground plate 12 is a collector plate 15. On the reverse side of the ground plate 12 from the cathode I3 is an outputtuned circuit 16 like the system 64, 65, 66 shown in Fig. 1'0". A- coupling loop IT is provided in inductive relation to the circuit 16 and is connected to a load l8.

In the operation of the arrangement of Fig. 11, the oscillator section is excited by the slower group of electrons as in the arrangement of Fig. 5 and the spent electrons of the slower grou are collected on the plate i5. The electrons of the faster group pass through the space between the plates 12 and 75 as in the arrangement of Figs. 9 and 10- where they serve to excite the tuned circuit 16 which in turn supplies oscillations to the load 18 through the coupling loop H. The load 18 may be varied without disturbing to any appreciable extent the operating conditions of the oscillator section. Therefore, the load has a minimum of disturbing effect upon the frequency of the oscillator.

Fig; 12 shows a modification of the tuned circuit of Fig. 5. The anode segments H and i3 of Fig. 5 are merged into a singlesegment its which may surround a middle segment ill! as shown. The inductive connection between the segments I Bil and It! comprises the conductors i4, i5 and I6 corresponding to those similarly numbered in Fig; 5.

Fig. 13 shows a tuned circuit similar to that of Fig. 12 but with the inductive connection between the plates [Gil and iii! simplified so as to eliminate the conductor !4.

Figs. 14 and 15 show tuned circuits similar in principle respectively to the tuned circuits of Figs. 12 and 13.

In the arrangement of Fig. 14, a conductive bar I62 takes the place of the conductors it, l5, 16, inclusive, of Fig. 12. In this kind of structure there is less inductance in the connector E02 and resonance is determined to a greater extent by distributed inductance in the segments I00 and 50!.

In the arrangement of Fig. 15 the inductive connection I5, it is replaced by a bar I83. Here again the inductance relied upon for resonance resides mainly in the distributed inductance of the segments Hill and I65.

Fig. 16 shows a tuned circuit comprising a pair of anode segments Hi4 and we joined by an inductive conductor we. The arrangement is mounted so that the plates I94 and 35 are coplanar with a guard plate Hill and are positioned man opening therein. The conductor 2% is conductively connected to and supported by a conductor m8 which is in turn conductively connected to and supported by the plate till. The conductor I08, while it may represent an appreciable inductance: can still. serve as an: untuned connection between the conductor its and the plate H31. It is only necessary that the system I01, [68 shall not support electromagnetic oscillations at a frequency in the neighborhood of the desired operating frequency. Under this condition, the anode segments Hi4 and 555 may sustain an alternating potential, while the plate it! and connector I08 will remain at a substantially unvarying potential.

Fig. 17 shows a tuned circuit which is a modification of that shown in Fig. 16. A guard plate Nil has two openings Within which the plates is! and H are positioned respectively. The conductor it?) connects the plates Hi4 and F35 as in Fig. 16 and a conductor Hi8 connects the middle of the conductor 96 to the portion of the plate l8? between the two openings.

In Fig. 18 is shown an arrangement generally similar to that of Fig. 11 and containing several added features. he tuned circuit l4 may be of the type shown in Fig. 1.7, the broken lines 86 and 8'! representing conductive connections eifected within the body of plate Hl'i' of Fig. 17. The. tuned circuit l5 may be of the type shown in Fig. 16, broken lines 3t, 87- and representing the conductor 1% of Fig. 16. The ground plate i2 is in two sections separated by a gap and connected by an untuned conductive connection 89. Opposite the gap in the plate 12 is provided a grid 9i? which may be used for modulation or other control purpose. An additional collector 9] is arranged in the plane of the plate 12. The crossed circle at the letter H is symbolic to represent the direction of the steady magnetic field, into the plane of the paper and parallel to the cathode '53. The steady magnetic field may be supplied by any suitable means (not shown) as, for example, an electromagnet as shown in Figs. 5 and 5A.

In the operation of the arrangement of Fig. 18, the tuned circuit M may be kept at a desired positive potential with respect to the plate l2. The tuned circuit it may be kept at a diilerent positive potential with respect to the plate '52.

. By properly arranging the spacing of the respective plates; the system may be operated with a higher potential inthe amplifier section than in the oscillator section, if desired.

Fig. 19 shows in longitudinal section an adaptation of the arrangement of Fig. 10 which enables the device to operate as a repeater in a wave guide transmission system. The wall of a wave guide is shown at 93. A resonant section of wave guide, preferably constituting a half wavelength resonator is defined by iris diaphragms represented schematically at 9 1 and 95. Diaphragm 94 may be variable as to the size of the aperture and diaphragm 95 may have a fixed aperture hermetically sealed by a window 96 of dielectric material. Similar elements 9%, 95 and 96' may be provided to determine another halfwave resonator and a chamber 9'! between the diaphragm 95 and 555. In the chamber 9? may be located a cathode 5!, a ground plate 54 and a collector 62, similar to the corresponding elements shown in Fig. 10.

In the operation of the arrangement of Fig. 19, the apertures in the diaphragms 95 and 95' correspond respectively to the gaps in the input and output tuned circuits of the arrangement of Fig. 10. A wave transmitted from left to right through the wave guide will be resonated in the chamber between the diaphragms 94 and 95 and will impress an alternating potential cross the input gap. The .output' potential will be impressed across the output gap and will act through the window 96, to set up an amplified wave in the resonator between the diaphragms 95 and 94. The amplified wave will be transmitted through the aperture of the diaphragm 94' and be propagated along to the right through the wave guide.

It will be suggested by inspection of the tuned circuits of Figs. 14 and 15 that other equivalent tuned circuits may be produced out of a plate alone without external connectors by providing suitable slots in the plate. The slots may be closed at the ends or they may be open, coming out to the edges of the plate. Fig. 20 shows an illustrative example of a system with a tuned circuit made by cutting slots in a plate. In Fig. 21, a similar result is secured by using suitably shaped segments which have their respective edges separated by a gap.

In the arrangement of Fig. 20 a single plate III! is provided with input and output slots III and H2 respectively which are open at one end. The plate IIO may be supported by an insulating post I I3, preferably located at a nodal point with respect to electromagnetic oscillations of the plate I II The configuration of the tuned circuit of Fig. 20 is such that the electric intensity at the gaps Ill and H2 is oppositely directed at any given instant as indicated by the polarity signs in the figure. Consequently, a transit time of an odd number of half cycles between the gaps III and H2 is required to meet the condition for sustained oscillations. This is in counterdistinction to the cases in which the electric intensities at the gaps are in the same sense at any given instant, in which case a transit time of an even number of half cycles is required. A suitably shaped coupling conductor II4 may be mounted parallel to the plate I ID for picking up oscillations to be transmitted to a load circuit. Fig. 20 also illustrates the use of an indirectly heated cathode II which may be in the form of a ribbon, strip or stripe of thermionically active substance inlaid, painted or otherwise disposed upon the surface of the ground plate. In this case the cathode may be heated by a separate heating conductor or in any suitable fashion.

Fig. 21 shows a tuned circuit comprising a T-shaped plate H5 and a U-shaped plate In. Distributed capacity is provided between the adjacent edges of the plates HE and III. The plates may be supported on insulating posts H8 and IIS, respectively, which are preferably located at points of unvarying potential in the plates. A coupling loop I 25 is provided in a plane parallel to the plates I I6 and I N.

Fig. 22 shows an oscillator structure generally similar to that shown in Fig. 5. The difference is that the inductive connection I4-I Ii, inclusive, is replaced by two similar inductive connections I2I and I22, near opposite ends of the anode segments, and a coupling loop I23 is placed be tween the conductors HI and I22 in inductive relation to both.

Fig. 23 illustrates another arrangement for coupling an oscillator to a wave guide. The oscillator, which is generally similar to that shown in Fig. 5 has a ground plate I33 comprising a disc fitting snugly into a hollow pipe wave guide I3I. The tuned circuit is indicated at I32. A coupling loop I33 is mounted in an insulating disc I34 which also fits snugly into the pipe Hi. The ends of the loop I33 extend through the disc I34 into the interior of an adjoining wave guide I38 to constitute a dipole I35. The pipe I3I may be evacuated and sealed off or it may be connected to a vacuum pumping system. In the latter case, the plate I30 is preferably provided with an aperture I31 through which the space between the discs I35 and I34 may be evacuated. The dipole I35 when actuated by the oscillator serves to set up traveling electro-magnetic waves within the wave guide I36.

Figs. 24 and 25 indicate how the arrangement of the invention may be adapted to utilize concentric cylindrical plates in place of plane parallel plates. A hollow cylindrical conductor I40 closed by conductive end plates MI and I42 serves in place of the plate I of Fig. 5. A cupshaped conductor I43 is mounted surrounding and spaced apart from the slotted portion of the conductor I40. Separated from the open end of the conductor I43 is placed a hollow conductive tube I44 of the same diameter and coaxial therewith. The ends of the conductors I43 and I44 are joined by an annular dielectric seal I45 which may be a fused glass ring. The inner and outer cylindrical assemblies described are held in place by another annular dielectric seal I46 which may also be a glass ring. Alternate segments of cylinder I 40, such as segments I41 and I48, for example, are joined to an unslotted portion I49 which forms the inner conductor of a coaxial transmission line of which the cylinder I44 is the outer conductor. Intermediate segments of cylinder I 40, such as I50 and I5I, for example, are conductively joined to the cylinder I44 by means of a conductive bridge member I52 which is formed to have clearance from the group of segments comprising l-4'I, I48.- The segments together with the coaxial line form a half-wave resonator short-circuited at one end by the end plate I4! and at the other end by an annular tuning plunger I53, the latter being adjustable in position by means comprising a knob I54.

A cathode I55 is insulatingly mounted in axial position on the inner surface of the cup I43. A collector plate I56 is insulatingly mounted parallel to and a short distance to one side of the cathode I 55. A suitable magnetic field in the axial direction is supplied by means such as an electromagnet coil I57. The resonator may be provided with a coaxial output lead I58.

The operation of the system of Figs. 24 and 25 is generally similar to that of Fig. 5. Besides the substitution of cylindrical for plane plates the number of gaps to be traversed by the slower group of electrons has been increased. The typical trajectory of an electron of the slower group is indicated by the broken line I59 which is a trochoidal curve of gradually decreasing amplitude of excursion in the radial direction. With proper adjustment of the electric and magnetic fields the electron may be made to contribute energy to the resonator at each gap. The static fields are to be so adjusted that the electron trajectories will curve away from the collector plate I56 as they first leave the cathode I55. The group of electrons that receive an acceleration at the first or input gap will strike the inner surface of the can I43 and be removed from the stream.

While means for supplying the necessary steady component of magnetic field are shown only in Fig. 5, it will be understood that suitable meansfor this purpose are to be supplied in each arrangement illustrated. Mechanical supports for the elements have also been omitted 1'? from several of the figures in the interest of focusing attention upon those features which form a part of the present invention.

What is claimed is:

l. A magnetron comprising two systems of coplanar plate electrodes located in parallel planes respectively, the first of said plate systems comprising three anode, segments defining between pairs of adjacent edges an input gap and an output gap respectively, said gaps extending parallel to each other, the second of said plate systems comprising a ground plate and a collector plate insulated from each other, a linearly extended cathode-substantially in the plane of said ground plate and oriented arallel to said input and output gaps, the distance between said input and output gaps being substantially 1r times the separation between said parallel planes, and the dis tance between the cathode and the input gap as projected upon said parallel planes being onehali the distance between said input and output gaps, and conductor means connected to said anode segments across said input and output gaps, respectively, and forming a resonant system.

2. An oscillator comprising aground plate, an anode plate system parallel to said ground plate and spaced therefrom a given distance a, said anode plate system comprising three coplanar segments having parallel adjacent edges defining an input'gap and an output gap, said gaps having their centers spaced apart a distance equal to- 1111, a cathode extending parallel to said input and output gaps and substantially coplanar with said ground plate, said cathode being a distance equal to from the projection of the said input gap upon said ground plate in the direction away from said output gap, a resonant system including said anode segments and coupling said input gap and said output gap, means adjacent to the space between said ground plate and said anode to maintain substantially constant crossed electric and magnetic fields in the space between said ground plate and said anode to constrain electrons from said cathode to follow trochoidal paths normally passing close to said input gap and said output gap, means including part of said resonant system to velocity vary the electron stream at said input gap whereby the faster electrons are made to strike said ground plate, and means including part of said resonant system to abstract energy from the slower electrons at said output gap.

3. An oscillator in accordance with claim 2 in which the said substantially constant electric field is uniformly directed perpendicular to the said parallel plates in the sense to impel electrons toward said anode system, and in which the said substantially constant magnetic field is uniformly directed parallel to said cathode and in which the given distance a in centimeters and the electric and magnetic field intensities E and M respectively in electromagnetic units are related according to th formula 2mc E eh,

where m is the mass of an electron in grams, e is the electronic charge in electromagnetic units and c is the velocity of light in centimeters per second.

4;. An oscillator comprising a ground plate, an

18 anode plate system parallel to said ground plate and spaced therefrom a distance a, said anode plate system comprising three coplanar segments having parallel adjacent edges defining an input gap and an output gap, said gaps having their centers spaced apart a distance equal to 1rd, a cathode extending parallel to said input and output gaps and substantially coplanar with said ground plate, said cathode being a distance equal to,

from the projection of the said input gap upon said ground plate on the side away from said output gap, a system resonant to a given wavelength A including said anode segments couplingsaid input gap and said output gap together to provide a feedback, substantially constant potential difierence means of V0 volts connected be tween said ground plate and said anode system and poled to impel electrons from said ground plate toward said anode system, means to maintain a substantially constant magnetic field of intensity H in said space in a direction parallel to said cathode and oled toturn toward the input gap electrons emitted from said cathode, said distance a being related to the wave-length according to the formula J y I O 3160 wheren is an integer and H' is determined by from the projection of one of said gaps upon said ground plate on the side away from the other of said gaps, substantially constant voltage supply means of voltage V0 connected between said ground plate and said anode system and poled to impel electrons from said ground plate toward said anode system, means adjacent to the space between said ground plate and said anode to maintain a substantiall constant magnetic field of intensity H in said space in a direction parallel to the axis of said cathode and poled to turn toward the nearest of said gaps electrons emitted from said cathode, the values of a, V0 and H being related in accordance with the formula a i V0 where m/e is the ratio of mass to charge for an electron and c is the velocity of light.

6. An oscillator comprising a cathode, a hollow pipe wave guide having for an end closure a conductive end plate containing a pair of slots defining an input gap and an output gap, respectively, said wave guide constituting a coupling between said input and output gaps, and said end plate being mounted opposite said cathode to constitute an anode therefor, means in 

